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Fullerenes with a single lanthanum atom trapped on the inside of the carbon cage were produced by laser vaporization of a lanthanum oxide/graphite composite rod in a flow of argon gas at 1200 °C. When sublimed with C_ (60) and C_ (70), they formed air-stable film containing principally LaC_ (60), LaC_ (70), LaC_ (74), and LaC_ (82). When dissolved in toluene and exposed to air, _ (82) was found to be uniquely stable. Evidence was also obtained for coalescence reactions between these fullerenes at temperatures to form larger cages with as many as three lanthanum atoms inside. Indications have also been obtained the successful production of KC_ (60), C_ (59) B, and KC_ (59) B where the boron has substituted for a carbon in the soccerball cage. use of the @ symbol is advocated for specifying such complex fullerenes as (K@C_ (59) B).
Chai et al. (Tue,) studied this question.